1. Field of the Invention
This invention relates to an agent for the separation and removal of proteins from blood plasma by the salting-out effect, and to an apparatus which utilizes the agent to separate and remove specific proteins such as immune complexes, immunoglobulins, fibrinogen and other soluble macromolecular proteins from blood plasma. The apparatus is used in removing pathogenic substances from a large quantity of collected blood followed by reinfusion of the blood, and in the purification of plasma by removal of pathogenic substances from a large quantity of pool blood.
2. Description of the Prior Art
It is becoming clear that immunoglobulins, immune complexes, complement, fibrinogen and other soluble macromolecular substances contained in blood play a role in causing autoimmune diseases, rheumatoid arthritis and other antigenic diseases. These diseases are treated by a plasma exchange process which includes removing plasma containing the harmful substances from the patient's blood and replacing the plasma with a substitute fluid. This process was first used in 1963 for the treatment of macroglobulinemia and since then has been tried in the treatment of many illnesses. With the development in recent years of membrane-type plasma separators, plasma exchange has become simpler and, hence, more widely practiced. However, the wider application of this treatment has been accompanied by increased consumption of the substitute fluids (e.g., FFP, agents made of albumin and the like) the supply of which has, as a result, become limited and higher in cost. An additional problem is that the infusion of a large quantity of human plasma can bring about unwelcome side effects such as hepatitis, alergic reactions and serum sickness.
A method now undergoing research for dealing with the foregoing problems is so-called plasma purification or cleansing which, rather than relying upon a substitute fluid, selectively removes the macromolecular proteins causing the particular illness from the patient's blood plasma and reinfuses the patient with his or her own cleansed blood plasma containing albumin and other useful plasma ingredients. Plasma purification processes known so far include a process for removing macromolecular protein from blood plasma by using a membrane having a pore diameter smaller than that of a plasma separating membrane, and a process for the adsoptive removal of macromolecular protein from blood plasma by relying upon an adsorbent. While the former has tentatively shown some efficacy in clinical use and has won some standing as a curative means, the latter is still in the basic research stage and only partial clinical use has been reported. Both processes have drawbacks in that the former exhibits insufficient selectivity in terms of removing specific proteins and the latter is incapable of treating a large quantity of plasma at one time. Thus, neither process is truly adequate. Accordingly, there is a need to develop a more effective and efficient apparatus for purifying blood plasma.
In view of these circumstances, the applicant has filed patent applications for inventions the gist of which is to use a chloride of an alkaline metal, e.g., sodium chloride, as an agent, or precipitating medium, for separating proteins from plasma by the salting-out effect. The applications filed are Japanese Patent Application Nos. 58-207463 and 58-207464. The proposed separating agent, owing to its weak salting-out action and low solubility in blood plasma, is effective in causing the specific precipitation solely of macromolecular proteins such as fibrinogen and immuno-globulins without resulting in the precipitation of such useful proteins of low molecular weight as albumin, even if the rate at which the agent is added to plasma is greater than that required for saturation.